The invention concerns a process for piecing a yarn on spinning assemblies of an open end spinning machine, and an open end spinning machine for execution of the process, in which a yarn end taken from a winding spool for the previously spun yarn is prepared for a piecing process, guided back into a spinning rotor, applied to a ring of silver that is present there, and again drawn off as new yarn, whereby the production of the silver ring in the spinning rotor, the application to this ring, and the drawing off of the new yarn occur before the previously braked spinning rotor reaches it operational rpm.
From German OS No. 2,321,775 (corresponding to U.S. Pat. No. 3,892,062), it is known that in an open end spinning machine, piecing can be effected by means of a mobile piecing device in which the control means for the devices that execute the piecing are adjusted to each other temporally, and to the running up phase of the previously braked spinning rotor, so that application and new drawing off of the yarn is effected during the running up curve of the spinning rotor. Here the circumstance is exploited that in running up, the spinning rotor passes through an rpm (rotational speed--revolutions per minute) range that is especially suitable for piecing, and this range is utilized for the piecing operation. Here there is the advantage that without a regulation of the rpm, and without reduction of the rpm of the whole spinning machine, a piecing operation can be effected at an advantageous rpm although the operational rpm may be distinctly higher.
In practice it has turned out that there are difficulties which are caused primarily by the switching and actuating times of the individual elements. These problems come up particularly in the case of small, correspondingly light spinning rotors. The invention concerns the problem of creating a process of the specified kind, whereby it will be possible to make available the necessary switching and actuating times for the individual steps of the piecing operation without the need for new types of drives or the like for the spinning assembly. The problem is solved in that the running up behavior of the spinning rotor is influenced so as to lengthen the time segment in which suitable rpm's of the rotor prevail for a piecing operation.
With this arrangement, there is more time for all work steps during the piecing process so that they do not hamper each other, and the most favorable conditions for piecing can be utilized.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.